Method and apparatus for signaling in dense network operations

ABSTRACT

A method, an apparatus, and a computer program product for wireless communication are provided. The apparatus receives an LDCS configuration for a UE relay from a second entity and monitors for an LDCS from the UE relay based on the received LDCS configuration. The second entity may comprise one of an LPN that is not in a dormant state and a Macro cell. The apparatus may receive LDCS configurations for a plurality of LPNs and monitor for a plurality of LPNs based on the received LDCS configurations. When the apparatus determines a need to connect to a LPN, the apparatus may select an LPN among the plurality of LPNs.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application Ser.No. 61/639,778, entitled “METHOD AND APPARATUS FOR SIGNALING IN DENSENETWORK OPERATIONS” and filed on Apr. 27, 2012, which is expresslyincorporated by reference herein in its entirety.

BACKGROUND

1. Field

The present disclosure relates generally to communication systems, andmore particularly, to a method and apparatus for energy efficientsignaling and operation in densely deployed networks.

2. Background

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includecode division multiple access (CDMA) systems, time division multipleaccess (TDMA) systems, frequency division multiple access (FDMA)systems, orthogonal frequency division multiple access (OFDMA) systems,single-carrier frequency division multiple access (SC-FDMA) systems, andtime division synchronous code division multiple access (TD-SCDMA)systems.

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is Long Term Evolution (LTE). LTE is a set ofenhancements to the Universal Mobile Telecommunications System (UMTS)mobile standard promulgated by Third Generation Partnership Project(3GPP). It is designed to better support mobile broadband Internetaccess by improving spectral efficiency, lower costs, improve services,make use of new spectrum, and better integrate with other open standardsusing OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), andmultiple-input multiple-output (MIMO) antenna technology. However, asthe demand for mobile broadband access continues to increase, thereexists a need for further improvements in LTE technology. Preferably,these improvements should be applicable to other multi-accesstechnologies and the telecommunication standards that employ thesetechnologies.

Dense network deployment can significantly improve wireless systemcapacity. In such dense network deployment, Low Power Nodes (LPN)provide service to other User Equipment (UE) in their vicinity. An LPNmay comprise a UE relay, a Remote Radio Head (RRH), a pico cell, femtocell, etc. A pico cell has a power of approximately 30 dBm, and a UErelay has a power of approximately 23 dBm. Thus, a “low” power node hasa power that is less than approximately 46 dB, which is the typicaltransmit power of a Macro cell. A UE relay is a UE that has both abackhaul link, e.g., to an eNB or other LPN, as well as an access linkfor another UE. Dense deployments may include a large number of LPNs.

Although the use of LPNs can greatly increase the capacity of thewireless system, such operations also place a strain on the battery ofthe LPN. Thus, there exists a need to ensure energy efficient operationof LPNs involved in such dense network deployment.

SUMMARY

In order to overcome the problems associated with dense networkdeployment, aspects presented herein enable an LPN, e.g., a UE relay,involved in dense network deployment to remain dormant wheneverrelay/LPN operation is not required. With a densely deployed network, itis likely that some of the LPNs will have periods without any associatedusers. For example, an LPN might not have any connected users or none ofthe connected users may be active. In this circumstance, it isadvantageous to reduce the transmit power or duty cycle of the LPN inorder to conserve energy. Aspects presented herein provide signaling andprocedures to enable such a reduction in transmit power or duty cycle.

In an aspect of the disclosure, an apparatus, method, and a computerprogram product are provided for wireless communication at a UE in adense network deployment. The apparatus receives a very low duty cyclesignal (LDCS) configuration for a UE relay from a second entity. A verylow duty cycle signal comprises a signal having a duty cycle with aninterval of hundreds of ms, a few seconds or even more depending on howmuch power saving is desired. The second entity may be anothernon-dormant LPN or a cell, e.g. a Macro cell, Pico cell or RRH. Afterreceiving the LDCS configuration, the apparatus monitors for an LDCSfrom the UE relay based on the received LDCS configuration.

Among others, the format of the LDCS may comprise at least one of aspecial synchronization signal format, an enhanced cell-specificreference signal (CRS) format, a coded signal transmission format, achannel state information reference signal (CSI-RS) format, and a systeminformation block (SIB) format. For example, the format of the LDCS maycomprise an SIB format having a reduced amount of information, whereinthe LDCS comprises at least one of SIB information and a global cell ID.

The LDCS configuration received from the second entity may be comprisedin any of, among others, a primary synchronization signal (PSS)transmission, a secondary synchronization signal (SSS) transmission, aphysical broadcast channel (PBCH) transmission, an SIB transmission, anda master information block (MIB) transmission from the second entity.

The UE may receive LDCS configurations for a plurality of LPNs from thesecond entity, the plurality of LPNs including the UE relay. The LPNsmay comprise, e.g., a UE relay, an RRH, or another type of LPN. Theapparatus may monitor a plurality of LDCSs based on the received LDCSconfigurations. When the apparatus determines a need to connect to anLPN, the apparatus selects an LPN among a plurality of LPNs.

In another aspect of the disclosure, an apparatus, method, and acomputer program product are provided for wireless communication of anLDCS configuration for a UE relay from a second entity. Similar to thefirst aspect, the second entity may be another LPN or a cell. Theapparatus identifies a UE relay and transmits an LDCS configuration ofthe UE relay. The apparatus may receive LDCS information for the UErelay, wherein the LDCS configuration is transmitted after the LDCSinformation is received. Alternatively, the apparatus may determine theLDCS configuration itself and thereafter transmit the LDCS configurationto the UE relay. The LDCS configuration transmitted from the secondentity may comprise at least one of a PSS, an SSS, a PBCH, an SIB, andan MIB, among others.

In another aspect of the disclosure, an apparatus, method, and acomputer program product are provided for wireless communication at a UErelay. In this aspect, the apparatus transitions to a dormant state andtransmits an LDCS while in the dormant state.

Aspects may further include transmitting an LDCS configuration to asecond entity, the second entity being one of an LPN that is not in adormant state and a Macro cell. The LDCS configuration may comprise,e.g., transmit power information for the LDCS.

Aspects may further include monitoring for a RACH message at apredetermined RACH delay after transmitting the LDCS. The predeterminedRACH delay may be comprised in the transmitted LDCS. The LDCS mayfurther comprise RACH configuration, wherein the RACH configurationrelates to a global cell ID. The LDCS may further comprise at least oneof backhaul quality information and loading capability information forthe UE relay.

The transition to the dormant state may be made from an active state,and the transition may be performed based at least in part on anexpiration of a predetermined period of time.

Aspects may further include monitoring at least one connected UE anddetermine whether any connected UE is active. The transition to thedormant state may be performed when no UEs are determined to be activefor the predetermined period of time.

Aspects may further include determining that no connected UEs of the UErelay are active, and when it is determined that no connected UEs of theUE relay are active, transitioning to a discontinuous reception andtransmission (DRX/DTX) mode, wherein the transition to the dormant stateis performed from the DRX/DTX mode.

Aspects may further include determining that no connected UEs areactive, wherein the UE relay transitions to the dormant state at thepredetermined period of time after determining that no connected UEs areactive.

Aspects may further include any of matching the DRX/DTX mode to aDRX/DTX mode for at least one connected UE, matching the DRX/DTX mode toa DRX/DTX mode for plurality of connected UEs, wherein the DRX/DTX modefor each of the connected UEs is different, and matching the DRX/DTXmode to a DRX/DTX mode for a plurality of connected UEs, wherein theDRX/DTX mode for each of the connected UEs is the same. The DRX/DTX modemay comprise a configuration for an access link of the UE relay and aconfiguration for a backhaul link of the UE relay. The configuration forthe access link of the UE relay may match the configuration of thebackhaul link of the UE relay. The configuration for the access link ofthe UE relay may be different than the configuration of the backhaullink of the UE relay.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture.

FIG. 2 is a diagram illustrating an example of an access network.

FIG. 3 is a diagram illustrating an example of a DL frame structure inLTE.

FIG. 4 is a diagram illustrating an example of an UL frame structure inLTE.

FIG. 5 is a diagram illustrating an example of a radio protocolarchitecture for the user and control planes.

FIG. 6 is a diagram illustrating an example of an evolved Node B anduser equipment in an access network.

FIG. 7 is a diagram illustrating a range expanded cellular region in aheterogeneous network.

FIG. 8 is a diagram illustrating a densely deployed network inaccordance with aspects presented herein.

FIG. 9 is a chart illustrating potential states of an LPN in accordancewith aspects presented herein.

FIG. 10 is a diagram illustrating aspects of DRX/DTX matching.

FIG. 11 is a diagram illustrating aspects of DRX/DTX matching.

FIG. 12 is a flow chart of a method of wireless communication.

FIG. 13 is a flow chart of a method of wireless communication.

FIG. 14 is a flow chart of a method of wireless communication.

FIG. 15 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 16 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 17 is a conceptual data flow diagram illustrating the data flowbetween different modules/means/components in an exemplary apparatus.

FIG. 18 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 19 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

FIG. 20 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing a processing system.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented withreference to various apparatus and methods. These apparatus and methodswill be described in the following detailed description and illustratedin the accompanying drawings by various blocks, modules, components,circuits, steps, processes, algorithms, etc. (collectively referred toas “elements”). These elements may be implemented using electronichardware, computer software, or any combination thereof. Whether suchelements are implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem.

By way of example, an element, or any portion of an element, or anycombination of elements may be implemented with a “processing system”that includes one or more processors. Examples of processors includemicroprocessors, microcontrollers, digital signal processors (DSPs),field programmable gate arrays (FPGAs), programmable logic devices(PLDs), state machines, gated logic, discrete hardware circuits, andother suitable hardware configured to perform the various functionalitydescribed throughout this disclosure. One or more processors in theprocessing system may execute software. Software shall be construedbroadly to mean instructions, instruction sets, code, code segments,program code, programs, subprograms, software modules, applications,software applications, software packages, routines, subroutines,objects, executables, threads of execution, procedures, functions, etc.,whether referred to as software, firmware, middleware, microcode,hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functionsdescribed may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on or encoded as one or more instructions or code on acomputer-readable medium. Computer-readable media includes computerstorage media. Storage media may be any available media that can beaccessed by a computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer. Disk and disc, as used herein, includescompact disc (CD), laser disc, optical disc, digital versatile disc(DVD), floppy disk and Blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

FIG. 1 is a diagram illustrating an LTE network architecture 100. TheLTE network architecture 100 may be referred to as an Evolved PacketSystem (EPS) 100. The EPS 100 may include one or more user equipment(UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS)120, and an Operator's IP Services 122. The EPS can interconnect withother access networks, but for simplicity those entities/interfaces arenot shown. As shown, the EPS provides packet-switched services, however,as those skilled in the art will readily appreciate, the variousconcepts presented throughout this disclosure may be extended tonetworks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108.The eNB 106 provides user and control planes protocol terminationstoward the UE 102. The eNB 106 may be connected to the other eNBs 108via a backhaul (e.g., an X2 interface). The eNB 106 may also be referredto as a base station, a base transceiver station, a radio base station,a radio transceiver, a transceiver function, a basic service set (BSS),an extended service set (ESS), or some other suitable terminology. TheeNB 106 provides an access point to the EPC 110 for a UE 102. Examplesof UEs 102 include a cellular phone, a smart phone, a session initiationprotocol (SIP) phone, a laptop, a personal digital assistant (PDA), asatellite radio, a global positioning system, a multimedia device, avideo device, a digital audio player (e.g., MP3 player), a camera, agame console, or any other similar functioning device. The UE 102 mayalso be referred to by those skilled in the art as a mobile station, asubscriber station, a mobile unit, a subscriber unit, a wireless unit, aremote unit, a mobile device, a wireless device, a wirelesscommunications device, a remote device, a mobile subscriber station, anaccess terminal, a mobile terminal, a wireless terminal, a remoteterminal, a handset, a user agent, a mobile client, a client, or someother suitable terminology.

The eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110includes a Mobility Management Entity (MME) 112, other MMEs 114, aServing Gateway 116, and a Packet Data Network (PDN) Gateway 118. TheMME 112 is the control node that processes the signaling between the UE102 and the EPC 110. Generally, the MME 112 provides bearer andconnection management. All user IP packets are transferred through theServing Gateway 116, which itself is connected to the PDN Gateway 118.The PDN Gateway 118 provides UE IP address allocation as well as otherfunctions. The PDN Gateway 118 is connected to the Operator's IPServices 122. The Operator's IP Services 122 may include the Internet,the Intranet, an IP Multimedia Subsystem (IMS), and a PS StreamingService (PSS).

FIG. 2 is a diagram illustrating an example of an access network 200 inan LTE network architecture. In this example, the access network 200 isdivided into a number of cellular regions (cells) 202. One or more lowerpower class eNBs 208 may have cellular regions 210 that overlap with oneor more of the cells 202. The lower power class eNB 208 may be a femtocell (e.g., home eNB (HeNB)), pico cell, micro cell, or remote radiohead (RRH). The macro eNBs 204 are each assigned to a respective cell202 and are configured to provide an access point to the EPC 110 for allthe UEs 206 in the cells 202. There is no centralized controller in thisexample of an access network 200, but a centralized controller may beused in alternative configurations. The eNBs 204 are responsible for allradio related functions including radio bearer control, admissioncontrol, mobility control, scheduling, security, and connectivity to theserving gateway 116.

The modulation and multiple access scheme employed by the access network200 may vary depending on the particular telecommunications standardbeing deployed. In LTE applications, OFDM is used on the DL and SC-FDMAis used on the UL to support both frequency division duplexing (FDD) andtime division duplexing (TDD). As those skilled in the art will readilyappreciate from the detailed description to follow, the various conceptspresented herein are well suited for LTE applications. However, theseconcepts may be readily extended to other telecommunication standardsemploying other modulation and multiple access techniques. By way ofexample, these concepts may be extended to Evolution-Data Optimized(EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interfacestandards promulgated by the 3rd Generation Partnership Project 2(3GPP2) as part of the CDMA2000 family of standards and employs CDMA toprovide broadband Internet access to mobile stations. These concepts mayalso be extended to Universal Terrestrial Radio Access (UTRA) employingWideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA;Global System for Mobile Communications (GSM) employing TDMA; andEvolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSMare described in documents from the 3GPP organization. CDMA2000 and UMBare described in documents from the 3GPP2 organization. The actualwireless communication standard and the multiple access technologyemployed will depend on the specific application and the overall designconstraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. Theuse of MIMO technology enables the eNBs 204 to exploit the spatialdomain to support spatial multiplexing, beamforming, and transmitdiversity. Spatial multiplexing may be used to transmit differentstreams of data simultaneously on the same frequency. The data steamsmay be transmitted to a single UE 206 to increase the data rate or tomultiple UEs 206 to increase the overall system capacity. This isachieved by spatially precoding each data stream (i.e., applying ascaling of an amplitude and a phase) and then transmitting eachspatially precoded stream through multiple transmit antennas on the DL.The spatially precoded data streams arrive at the UE(s) 206 withdifferent spatial signatures, which enables each of the UE(s) 206 torecover the one or more data streams destined for that UE 206. On theUL, each UE 206 transmits a spatially precoded data stream, whichenables the eNB 204 to identify the source of each spatially precodeddata stream.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas. To achieve good coverage at the edges of the cell, asingle stream beamforming transmission may be used in combination withtransmit diversity.

In the detailed description that follows, various aspects of an accessnetwork will be described with reference to a MIMO system supportingOFDM on the DL. OFDM is a spread-spectrum technique that modulates dataover a number of subcarriers within an OFDM symbol. The subcarriers arespaced apart at precise frequencies. The spacing provides“orthogonality” that enables a receiver to recover the data from thesubcarriers. In the time domain, a guard interval (e.g., cyclic prefix)may be added to each OFDM symbol to combat inter-OFDM-symbolinterference. The UL may use SC-FDMA in the form of a DFT-spread OFDMsignal to compensate for high peak-to-average power ratio (PAPR).

FIG. 3 is a diagram 300 illustrating an example of a DL frame structurein LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames.Each sub-frame may include two consecutive time slots. A resource gridmay be used to represent two time slots, each time slot including aresource block. The resource grid is divided into multiple resourceelements. In LTE, a resource block contains 12 consecutive subcarriersin the frequency domain and, for a normal cyclic prefix in each OFDMsymbol, 7 consecutive OFDM symbols in the time domain, or 84 resourceelements. For an extended cyclic prefix, a resource block contains 6consecutive OFDM symbols in the time domain and has 72 resourceelements. Some of the resource elements, as indicated as R 302, 304,include DL reference signals (DL-RS). The DL-RS include Cell-specific RS(CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS)304. UE-RS 304 are transmitted only on the resource blocks upon whichthe corresponding physical DL shared channel (PDSCH) is mapped. Thenumber of bits carried by each resource element depends on themodulation scheme. Thus, the more resource blocks that a UE receives andthe higher the modulation scheme, the higher the data rate for the UE.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structurein LTE. The available resource blocks for the UL may be partitioned intoa data section and a control section. The control section may be formedat the two edges of the system bandwidth and may have a configurablesize. The resource blocks in the control section may be assigned to UEsfor transmission of control information. The data section may includeall resource blocks not included in the control section. The UL framestructure results in the data section including contiguous subcarriers,which may allow a single UE to be assigned all of the contiguoussubcarriers in the data section.

A UE may be assigned resource blocks 410 a, 410 b in the control sectionto transmit control information to an eNB. The UE may also be assignedresource blocks 420 a, 420 b in the data section to transmit data to theeNB. The UE may transmit control information in a physical UL controlchannel (PUCCH) on the assigned resource blocks in the control section.The UE may transmit only data or both data and control information in aphysical UL shared channel (PUSCH) on the assigned resource blocks inthe data section. A UL transmission may span both slots of a subframeand may hop across frequency.

A set of resource blocks may be used to perform initial system accessand achieve UL synchronization in a physical random access channel(PRACH) 430. The PRACH 430 carries a random sequence and cannot carryany UL data/signaling. Each random access preamble occupies a bandwidthcorresponding to six consecutive resource blocks. The starting frequencyis specified by the network. That is, the transmission of the randomaccess preamble is restricted to certain time and frequency resources.There is no frequency hopping for the PRACH. The PRACH attempt iscarried in a single subframe (1 ms) or in a sequence of few contiguoussubframes and a UE can make only a single PRACH attempt per frame (10ms).

FIG. 5 is a diagram 500 illustrating an example of a radio protocolarchitecture for the user and control planes in LTE. The radio protocolarchitecture for the UE and the eNB is shown with three layers: Layer 1,Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer andimplements various physical layer signal processing functions. The L1layer will be referred to herein as the physical layer 506. Layer 2 (L2layer) 508 is above the physical layer 506 and is responsible for thelink between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control(MAC) sublayer 510, a radio link control (RLC) sublayer 512, and apacket data convergence protocol (PDCP) 514 sublayer, which areterminated at the eNB on the network side. Although not shown, the UEmay have several upper layers above the L2 layer 508 including a networklayer (e.g., IP layer) that is terminated at the PDN gateway 118 on thenetwork side, and an application layer that is terminated at the otherend of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radiobearers and logical channels. The PDCP sublayer 514 also provides headercompression for upper layer data packets to reduce radio transmissionoverhead, security by ciphering the data packets, and handover supportfor UEs between eNBs. The RLC sublayer 512 provides segmentation andreassembly of upper layer data packets, retransmission of lost datapackets, and reordering of data packets to compensate for out-of-orderreception due to hybrid automatic repeat request (HARQ). The MACsublayer 510 provides multiplexing between logical and transportchannels. The MAC sublayer 510 is also responsible for allocating thevarious radio resources (e.g., resource blocks) in one cell among theUEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNBis substantially the same for the physical layer 506 and the L2 layer508 with the exception that there is no header compression function forthe control plane. The control plane also includes a radio resourcecontrol (RRC) sublayer 516 in Layer 3 (L3 layer). The RRC sublayer 516is responsible for obtaining radio resources (i.e., radio bearers) andfor configuring the lower layers using RRC signaling between the eNB andthe UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650in an access network. In the DL, upper layer packets from the corenetwork are provided to a controller/processor 675. Thecontroller/processor 675 implements the functionality of the L2 layer.In the DL, the controller/processor 675 provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to the UE650 based on various priority metrics. The controller/processor 675 isalso responsible for HARQ operations, retransmission of lost packets,and signaling to the UE 650.

The transmit (TX) processor 616 implements various signal processingfunctions for the L1 layer (i.e., physical layer). The signal processingfunctions includes coding and interleaving to facilitate forward errorcorrection (FEC) at the UE 650 and mapping to signal constellationsbased on various modulation schemes (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded andmodulated symbols are then split into parallel streams. Each stream isthen mapped to an OFDM subcarrier, multiplexed with a reference signal(e.g., pilot) in the time and/or frequency domain, and then combinedtogether using an Inverse Fast Fourier Transform (IFFT) to produce aphysical channel carrying a time domain OFDM symbol stream. The OFDMstream is spatially precoded to produce multiple spatial streams.Channel estimates from a channel estimator 674 may be used to determinethe coding and modulation scheme, as well as for spatial processing. Thechannel estimate may be derived from a reference signal and/or channelcondition feedback transmitted by the UE 650. Each spatial stream isthen provided to a different antenna 620 via a separate transmitter618TX. Each transmitter 618TX modulates an RF carrier with a respectivespatial stream for transmission.

At the UE 650, each receiver 654RX receives a signal through itsrespective antenna 652. Each receiver 654RX recovers informationmodulated onto an RF carrier and provides the information to the receive(RX) processor 656. The RX processor 656 implements various signalprocessing functions of the L1 layer. The RX processor 656 performsspatial processing on the information to recover any spatial streamsdestined for the UE 650. If multiple spatial streams are destined forthe UE 650, they may be combined by the RX processor 656 into a singleOFDM symbol stream. The RX processor 656 then converts the OFDM symbolstream from the time-domain to the frequency domain using a Fast FourierTransform (FFT). The frequency domain signal comprises a separate OFDMsymbol stream for each subcarrier of the OFDM signal. The symbols oneach subcarrier, and the reference signal, is recovered and demodulatedby determining the most likely signal constellation points transmittedby the eNB 610. These soft decisions may be based on channel estimatescomputed by the channel estimator 658. The soft decisions are thendecoded and deinterleaved to recover the data and control signals thatwere originally transmitted by the eNB 610 on the physical channel. Thedata and control signals are then provided to the controller/processor659.

The controller/processor 659 implements the L2 layer. Thecontroller/processor can be associated with a memory 660 that storesprogram codes and data. The memory 660 may be referred to as acomputer-readable medium. In the UL, the controller/processor 659provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 662, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 662 for L3 processing. Thecontroller/processor 659 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets tothe controller/processor 659. The data source 667 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the eNB 610, thecontroller/processor 659 implements the L2 layer for the user plane andthe control plane by providing header compression, ciphering, packetsegmentation and reordering, and multiplexing between logical andtransport channels based on radio resource allocations by the eNB 610.The controller/processor 659 is also responsible for HARQ operations,retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a referencesignal or feedback transmitted by the eNB 610 may be used by the TXprocessor 668 to select the appropriate coding and modulation schemes,and to facilitate spatial processing. The spatial streams generated bythe TX processor 668 are provided to different antenna 652 via separatetransmitters 654TX. Each transmitter 654TX modulates an RF carrier witha respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar tothat described in connection with the receiver function at the UE 650.Each receiver 618RX receives a signal through its respective antenna620. Each receiver 618RX recovers information modulated onto an RFcarrier and provides the information to a RX processor 670. The RXprocessor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. Thecontroller/processor 675 can be associated with a memory 676 that storesprogram codes and data. The memory 676 may be referred to as acomputer-readable medium. In the UL, the control/processor 675 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the UE 650. Upper layer packets fromthe controller/processor 675 may be provided to the core network. Thecontroller/processor 675 is also responsible for error detection usingan ACK and/or NACK protocol to support HARQ operations.

FIG. 7 is a diagram 700 illustrating a densely deployed network. An LPN,e.g., a lower power class eNB such as RRH 710 b or UE Relay 710 c, orFemto cells, or pico cells can provide an access link for UE 720 inaddition to eNB 710 a.

The LPN may have a range expanded cellular region 703 that is expandedfrom the cellular region 702 through enhanced inter-cell interferencecoordination between the RRH 710 b and the macro eNB 710 a and throughinterference cancelation performed by the UE 720. In enhanced inter-cellinterference coordination, the RRH 710 b receives information from themacro eNB 710 a regarding an interference condition of the UE 720. Theinformation allows the RRH 710 b to serve the UE 720 in the rangeexpanded cellular region 703 and to accept a handoff of the UE 720 fromthe macro eNB 710 a as the UE 720 enters the range expanded cellularregion 703.

Through the use of LPNs providing service to UEs, dense networkdeployment improves wireless system capacity. However, among otherissues, such additional use of an LPN places an additional burden on itsbattery and power consumption.

In order to ensure energy efficient operation of LPNs involved in densenetwork deployment, the LPN should remain dormant whenever relayoperation is not required. For example, in a densely deployed network, anumber of LPNs will likely not have any connected and/or active usersassociated with them for certain periods of time. For a UE relay, it ispossible at times that no other UEs will be within the vicinity of theUE relay. At these times, the LPN can enter a dormant mode, or a dormantstate, during which the LPN transmits only an LDCS. A very low dutycycle signal comprises a signal having a duty cycle with an interval ofat least hundreds of ms. The interval may be set at a few seconds oreven more depending on how much power saving is desired. The sparsetransmission reduces the amount of DL interferences.

Among others, the format of the LDCS may comprise at least one of aspecial synchronization signal format, e.g., PSS/SSS, an enhanced CRSformat, a coded signal transmission format, a CSI-RS format, and a SIBformat.

For example, the format of the LDCS may comprise an SIB format having areduced amount of information, wherein the LDCS comprises at least oneof SIB information and a global cell ID. As another example, theenhanced CRS format for an LDCS signal may have a low duty cycle and mayspan, e.g., five RB, 25 resource blocks (RB), the entire systembandwidth, etc. As another example, the LDCS may comprise a coded signaltransmission having a low re-use preamble with encoded informationinside it. Such a coded signal transmission may be similar to a lowreuse preamble, such as used with D2D. The information encoded in thepreamble may include, e.g., a global cellular ID, an RACH delay inrelation to the LDCS, etc.

FIG. 8 illustrates LPN1 806 a, LPN2 806 b, and LPN3 806 c in a denselydeployed network overlapping with cell 802.

An LPN 806 a-c may have at least two different states, as illustrated inFIG. 9.

The LPN may have at least one connected state, such as connected activestate 902, and a dormant state 904. During the active state, the LPN hasactive UEs to serve. The LPN may transmit all necessary signals for datacommunications, such as demodulation reference signals (DMRS) fordemodulation, CSI-RS, CRS, CSI, PSS/SSS for synchronization, otherpossible uplink signals, and possibly special synchronization signal.During an active state for a UE relay, the UE relay has at least one UEconnected in active transmission. The UE relay may continuously monitoran UL and transmit any necessary signals on the DL.

During its dormant state 904, the LPN may transmit only LDCS signals. Adormant UE relay does not have any UEs associated with it. The dormantUE relay merely transmits a LDCS or does not transmit a signal at all,if it does not want to serve as a UE relay. An LDCS comprises aninterval of approximately hundreds of ms or more, e.g., on the intervalof a second or more. For example, an LDCS may be on an interval ofapproximately 300 ms. UEs in the proximity may detect the LDCS in orderto identify the presence of the nearby LPN. This enables the UE toinitiate the connection to the LPN while the LPN is in the dormantstate. By allowing the UE to remain in the dormant state without a lossin its ability to receive an indication of a need for service from a UEenables power efficiency for the operation of the LPN. In this way, theLPN avoids interference and wasting power by unnecessarily broadcastingsignaling with a higher duty cycle when there are no active UEs withinits vicinity.

The LPN may also include a third state, also referred to as a connectedDiscontinuous Reception and Transmission (DRX/DTX) state 906. A DRX/DTXstate for a UE relay, e.g., may comprise the UE relay being connected toat least one UE, where the UE is in a DRX mode. The LPN enters theDRX/DTX state when there is a reduced need for access. For example, theLPN may monitor its connected users to determine whether any of them areactive. If there are no users, or no active users, the LPN maytransition to the DRX/DTX state before transitioning to the dormantstate. Likewise, if the LPN determines that it is associated with alimited number of UEs and the limited number of UEs are in a DRX state,then the LPN may enter a DTX/DRX state. The LPN may match its DRX/DTXcycle with the UE's DRX cycle in order to maximize the power efficiencyof the LPN in this state.

While a DRX/DTX state may not be critical for an RRH, a pico cell, orother LPN that plugs into the wall, this state may be very important fora UE relay in order to extend its battery life.

As illustrated in FIG. 9, the LPN may transition from dormant 904 toactive 902 in response to an eNB requested activation and/or based onreceiving an RACH message from a UE in response to the LDCS.

The LPN may automatically transition from the active state 902 into adormant state 904. For example, the LPN may continuously monitor itsconnected users while in the active state. When certain criteria aremet, e.g., none of the users being active, the LPN may transition into adormant state upon the expiration of an inactivity timer. Among others,the criteria for such a transition may be based on whether the LPN hasany connected users, whether any of the connected users are active,whether the LPN has more than a predetermined number of connected and/oractive users, and a state of the battery of the LPN. For example, if theLPN does not have enough connected and/or active users, the LPN may handits current users over to another LPN in order to transition to adormant state. The LPN may also hand its current users over to anotherLPN and transition to a dormant state when its battery power drops belowa certain level.

The LPN may automatically transition from the active state 902 to aDRX/DTX state. Similar to the automatic transition from active todormant, in this case the LPN may transition into a DRX/DTX state uponthe expiration of an inactivity timer after a certain criteria is met.Similar criteria may be applied as for the transition from the activestate directly to the dormant state. In addition, the criteria mayinclude whether connected users are in a DRX mode. The DRX/DTX state isan intermediate state that uses less power than the active state, yetmore resources than the dormant state.

As illustrated in FIG. 9, the LPN might transition from DRX/DTX state906 directly back to an active state 902, e.g., if a packet arrives at auser or the LPN. The LPN may transition from the DRX/DTX state to thedormant state, e.g., upon the expiration of another inactivity timer.

Also illustrated in FIG. 9, the LPN may transition from the dormantstate 904 to the intermediate DRX/DTX state 906, e.g., upon a possiblepacket arrival.

Separate DRX and DTX configurations may be applied for an access linkand a backhaul link of the LPN. As the LPN may handle multiple users onseparate access links and a single backhaul, this enables an increasedperiodicity for the DRX/DTX on the access link in order to handle themultiple users. Thus, the LPN may transition into s DRX/DTX modeseparately for a backhaul link and an access link. The LPN maytransition into a DRX/DTX state for one or both links. Furthermore, theDRX/DTX configurations for both links may have different configurations.

The DRX/DTX configuration for the access link and the backhaul link maybe matched in order to preserve energy. This enables the LPN tocommunicate with both the UE and a base station using the sameperiodicity. Likewise, this configuration may be matched to a connectedUE's DRX/DTX.

For example, FIG. 10 illustrates the DTX operation for an LPN beingmatched to a DRX of a UE. Similarly, FIG. 11 illustrates the DRXoperation of the LPN being matched to the DTX of a UE.

Additionally, a cell, such as a macrocell may have a different DRX/DTXconfiguration for multiple LPNs on the backhaul in order to bettermultiplex different LPNS. For example, the macrocell may serve multipleUEs, UE relays, and other LPNs. The macrocell may have a differentconfiguration for each of these types of users in order to maximizeefficiency for each of them.

In order to enable a UE to receive an LDCS, a second entity assists theUE in receiving the LDCS. Among others, the second entity may be anotherLPN that is not in a dormant state, a cell that is continuouslytransmitting, and another anchor entity. Although the second entity mayalso be another type of anchor entity, an example will be describedapplying a macrocell as the second entity.

As illustrated in FIG. 8, macrocell 802 may transmit an LDCSconfiguration for each of LPNs 806 a-c. The LDCS configuration maycomprise, among others, any of PSS, SSS, PBCH, SIB, and MIB. A UE 804 areceives the LDCS configuration and uses it to monitor for an LDCS fromany of the LPNs to which it is close. While in an idle mode, the UEmonitors the LDCS from at least one LPN. The UE may perform proceduressimilar to cell reselection, as described in Release 8, i.e., it doesnot connect to any of the LPNs, but merely monitors them.

When the UE determines that it is in need of a data connection, the UEselects an LPN. Once an LPN is selected, the UE transmits an RACHmessage to the LPN. As the LPN is in a dormant state, the LPN is notcontinuously monitoring for transmissions from a UE. Thus, the UE needsto transmit the RACH message at a time when the LPN will be monitoringfor such messages. Thus, the UE transmits the RACH message at apredetermined amount of time, i.e. a predetermined RACH delay, afterreceiving the LDCS. After transmitting the LDCS, the LPN will monitorfor any RACH messages at the time indicated by the predetermined RACHdelay. For example, when the LPN transmits an LDCS at subframe n and hasa corresponding RACH delay of K, at time n+K, the LPN will look for anRACH sequence having a particular configuration. At all other times, theLPN may remain dormant. This deterministic delay ensures further powerefficiency while maintaining the potential for communication between theLPN and potential users. The RACH delay, K, may be signaled from themacrocell, e.g., along with the LDCS configuration information in anSIB/MIB. The RACH delay, K, and configuration may also be signaled tothe user directly from the LPN, such as inside the LDCS. Furthermore,the RACH configuration may be either linked to the global cell ID orspecified in LDCS configuration, or directly signaled by LDCS. This willallow the LPN to know that the UE is trying to access this particularLPN rather than any other nearby LPN.

FIG. 12 is a flow chart 1200 of a method of wireless communication at aUE. Optional aspects are illustrated with a dashed line. The method maybe performed by a UE. At step 1202, an LDCS configuration is receivedfor a UE relay from a second entity. This step may include receiving aplurality of LDCS configurations from the second entity at 1203, theconfigurations corresponding to a plurality of LPNs, including the UErelay. An LPN may be any of a UE relay, an RRH, and other types of LPNs.A low power node has a power less than approximately 46 dBm. Amongothers, the second entity may be an LPN that is not in a dormant stateand a cell, such as a Macro cell.

At 1204, the UE monitors for an LDCS from the UE relay based on thereceived LDCS configuration. If the UE has received LDCS configurationsfor additional LPNs, the UE may monitor for a plurality of LDCSscorresponding to the UE relay and the additional LPNs. The UE maymonitor for the LDCS during an idle mode or an active mode for the UE.This may be performed, e.g., in order to perform a possible dataconnection through the UE relay.

Among others, the format of the LDCS may comprise at least one of a SSSformat, an enhanced CRS signal format, a coded signal transmissionformat, a CSI-RS format, and a SIB format.

For example, the format of the LDCS may include an SIB format having areduced amount of information, such as where the LDCS comprises at leastone of SIB information and a cell ID. In a typical network multiple SIB,e.g. SIB1, SIB2, . . . , SIBn would be sent, each SIB specifying variousaspects, such as cell configuration, neighbor cell information, interRAT handover information, etc. In contrast, the SIB having a reducedamount of information could comprise a single SIB transmission havingall of the essential information for the low power node. Such an SIBtransmission may be termed an SIB lite. Thus, the LDCS in this examplecould just transmit the SIB lite information. This essential informationcomprises the information needed for a UE to access the LPN, such as theinformation needed to send a RACH message to the LPN.

The format of the LDCS may include an enhanced CRS having a low dutycycle and spans any of five RB, 25 resource blocks (RB) or the entiresystem bandwidth. The format of the LDCS may include a coded signaltransmission having a low re-use preamble comprising encodedinformation. A typical synchronization signal occurs every 5-10 ms, andan MIB approximately every 40 ms. Thus, a low re-use preamble may be onthe order of approximately one hundred ms or above. The format of theLDCS may comprise, e.g., a signal transmission having a low re-usepreamble comprises encoded information of a global cell ID and/or RACHconfiguration.

The LDCS configuration that is sent by the second entity may comprise,among others, a PSS, SSS, PBCH, SIB, and MIB transmission from thesecond entity.

When the UE receives the LDCS configurations for a plurality of LPNs,the UE monitors for a plurality of LDCSs from the plurality of LPNsbased on the received LDCS configurations. This enables the UE to selectan LPN from among the plurality of LPNs when it determines a need toconnect to an LPN 1206.

The selection 1206 of a particular LPN may be based on a number ofconsiderations.

For example, a node may be selected, e.g., based on the node with thelargest received power from its LDCS or based on the node with thesmallest path loss. Using the largest receive power, ensures the bestserving node from the DL perspective, whereas using the smallest pathloss ensures the best serving node from the UL perspective.

In order to measure path loss, the transmit power of the LDCS will needto be signaled to the UE. The UE will then be able to calculate ordetermine the path loss 1212 based on the signaled transmit power of theLDCS and the received power of the LDCS. This may be signaled from thesecond entity, e.g., from a macrocell 1208. The macrocell may signal thetransmit power along with other LDCS configurations in an SIB/MIB.Alternatively, the transmit power may be signaled as a part of the LDCSfrom the LPN 1210. For example, the transmit power of the LDCS may beembedded in the coded content of the LDCS or embedded as a portion ofthe sequence or configuration of the LDCS. Thus, the UE may receive atransmit power for the plurality of LPNs from, e.g., the second entity,the transmit power for each of the LPNs being comprised in the receivedLDCS configuration for the corresponding LPN. Then, the UE may determinea path loss for each of the plurality of LPNs based at least in part onthe received transmit power for the corresponding LPNs. In anotheraspect, each LDCS may comprise a transmit power for the correspondingLPN, and the UE may determine a path loss for each of the plurality ofLPNs based at least in part on the received transmit power for thecorresponding LPN.

An LPN may further indicate, among other features, its backhaul qualityand/or loading capability. The backhaul quality and/or loadingcapability may be embedded in the LDCS transmitted by the LPN orsignaled together with the LDCS configurations.

Once the backhaul quality and/or loading capability are received by aUE, e.g., at 1214/1216, the UE may use the information in its selectionof an LPN. For example, the UE may determine its own buffer status 1218and determine whether to access a particular LPN based on its bufferstatus and the received backhaul quality of the LPN. The UE may receivean LDCS from a plurality of LPNs based on the received LDCSconfigurations from the second entity. When the LDCS for each of theLPNs comprises at least one of backhaul quality information and loadingcapability information for the corresponding LPN, the UE may determinewhether to access any of the plurality of LPNs based on at least one ofthe received backhaul quality information and the loading capabilityinformation for the corresponding LPN in combination with the determinedbuffer status of the UE.

The UE may also use additional characteristics in its selection of anLPN. For example, the UE may determine whether to access any of aplurality of LPNs by jointly considering any of the backhaul quality ofthe LPN, the loading capability of the LPN, a received signal strength,a path loss, and a buffer status of the UE in order to determine whetherto access a particular LPN.

Once an LPN is selected, the UE transmits an RACH message to theselected LPN 1224 at an RACH delay after receiving the LDCS from theselected LPN. The RACH delay may be received by the UE from the secondentity 1208. For example, the LPN may have the RACH delay comprised inthe LDCS configuration for the selected LPN. This RACH delay might alsobe received from the selected LPN 1222. For example, the LPN may havethe RACH delay comprised in the LDCS.

The RACH message may also be transmitted to the selected LPN using anRACH configuration linked to the selected LPN after receiving the LDCSfrom the selected LPN, wherein the RACH configuration is comprised in atleast one of the LDCS received from the selected LPN the LDCSconfiguration received from the selected LPN. By using the RACHconfiguration linked to the selected LPN, the UE ensures that the LPNwill understand which LPN the UE is attempting to reach with the RACHmessage, or to which LPN the RACH message is intended.

The RACH configuration may be signaled in either the LDCS or the LDCSconfiguration for a specific LPN. The RACH configuration may relate to,or be tied to, a global cell ID so that when the UE transmits the RACH,the intended LPN knows that the UE is attempting to signal it via a RACHmessage.

FIG. 13 illustrates a diagram for a method 1300 of communication of LDCSconfiguration for a UE relay from a second entity. Optional aspects areillustrated with a dashed line. The method is performed by the secondentity, which may be another LPN that is not in a dormant state or aMacro cell. The second entity may correspond to the second entitydescribed in connection with FIGS. 12 and 14.

At step 1302 a UE relay is identified. The second entity may alsoidentify additional LPNs at 1303. Thus, the second entity may identify aplurality of LPNs, the plurality of LPNs including the UE relay. Asillustrated at 1304 and 1306, LDCS information for the UE relay mayeither be received by the second entity or configured by the secondentity itself. When the LDCS information is received by the secondentity, the LDCS configuration is transmitted 1308 after the LDCSinformation is received 1304. When the second entity configured the LDCSconfiguration 1306, the second entity also transmits the LDCSconfiguration to the UE relay 1310.

Potential formats for transmissions of the LDCS and the LDCSconfiguration may be the same as those described in connection with FIG.12.

The second entity may transmit a transmit power for the UE relay 1312,e.g., in an SIB/MIB transmission, in order to enable a path lossdetermination regarding the UE relay.

At step 1314, the cell may transmit an RACH delay relating to the LDCSfor the UE relay.

At 1316, the cell may configure a DRX/DTX mode for a backhaul for the UErelay. A DRX/DTX mode related to an additional LPN may be configured,with the DRX/DTX modes for the UE relay and the additional LPN beingdifferent in order to provide better multiplexing.

At 1318, a DRX/DTX mode for a UE may be configured, with the DRX/DTXmode for the UE relay and the DRX/DTX mode for the UE being different.The second entity may also configure the backhaul for the UE relay to aDRX/DTX matching an access link DRX/DTX configuration for the UE relay.Additionally, the second entity may configure the backhaul for the UErelay to a DRX/DTX to match an access link DRX/DTX configuration for theUE relay, and may configure the DRX/DTX configuration for the backhauland the access link DRX/DTX configuration to map to the DRX/DTXconfiguration for the UE.

The method may further include transmitting a RACH delay to a UE in theLDCS configuration for the UE relay.

In addition to a RACH delay, RACH configuration may be signaled from themacrocell, e.g., in the LDCS configuration for a specific LPN. The RACHconfiguration may relate to, or be tied to, a global cell ID so thatwhen the UE transmits the RACH, the intended LPN knows that the UE isattempting to signal it via a RACH message.

This enables the UE to transmit a RACH message to a selected LPN, fromamong a plurality of LPNs, using an RACH configuration linked to theselected LPN after receiving the LDCS from the selected LPN, wherein theRACH configuration is comprised in at least one of the LDCS receivedfrom the selected LPN and the LDCS configuration received from theselected LPN. By using the RACH configuration linked to the selectedLPN, the UE ensures that the LPN will understand which LPN the UE isattempting to reach with the RACH message, or to which LPN the RACHmessage is intended.

FIG. 14 illustrates a diagram for a method 1400 of wirelesscommunication at a UE relay. Optional aspects are illustrated with adashed line. The method may be performed by an LPN, as described herein,e.g., by a UE relay. At step 1408, the UE relay transitions to a dormantstate. At 1410, the UE relay transmits an LDCS while in the dormantstate.

Potential formats for the LDCS are described in connection with FIG. 12.The LDCS may optionally include transmit power information for the LDCS.

The UE relay may transmit an LDCS configuration to a second entity at1411 so that the second entity may transmit such LDCS configurationinformation for the UE relay while the UE relay is in the dormant state.The second entity may be, e.g., another LPN that is not in a dormantstate and a Macro cell.

At 1412, the UE relay monitors for an RACH message at a predetermined

RACH delay after transmitting the LDCS. The predetermined RACH delay maybe comprised in the transmitted LDCS or in the LDCS configuration. TheLDCS may further comprise at least one of backhaul quality informationand loading capability information for the UE relay.

In addition to a RACH delay, a RACH configuration may be signaled ineither the LDCS or the LDCS configuration. The RACH configuration mayrelate to, or be tied to, a global cell ID for the UE relay so that whena UE responds by transmitting the RACH, the intended UE relay knows thatthe UE is attempting to signal it via a RACH message. In an alternative,the RACH configuration for the UE relay may be signaled to the UE by asecond entity.

The transition to the dormant state 1408 may be made directly from anactive state and may be performed based at least in part on anexpiration of a predetermined period of time. For example, the UE relaymay monitor at least one connected UE at 1402. At 1404, the UE relay maythen determine whether any connected UE are active. The UE relayperforms the transition to the dormant state when no UEs are determinedto be active for the predetermined period of time.

When it is determined that the UE relay has no connected, active UEs,the UE relay may transition to a DRX/DTX mode at 1406 beforetransitioning to the dormant state. Thus, in this situation, thetransition to the dormant state is performed from the DRX/DTX mode.

When it is determined that the LPN has no connected, active UEs, the UErelay may transition to the dormant state at the predetermined period oftime after determining that no connected UEs are active.

As a part of transitioning to a DRX/DTX mode, the UE relay may match theDRX/DTX mode to a DRX/DTX mode for at least one connected UE at 1414.The UE relay may match the DRX/DTX mode to a DRX/DTX mode for pluralityof connected UEs, wherein the DRX/DTX mode for each of the connected UEsis different. The UE relay may match the DRX/DTX mode to a DRX/DTX modefor a plurality of connected UEs, wherein the DRX/DTX mode for each ofthe connected UEs is the same. Although the DRX/DTX matching have beendescribed using the example of a UE relay, such DRX/DTX matching mayalso be performed for another type of LPN.

The DRX/DTX mode may comprise a configuration for an access link of theUE relay and a configuration for a backhaul link of the UE relay. Theconfiguration for the access link of the UE relay may match theconfiguration of the backhaul link of the UE relay. The configurationfor the access link of the UE relay may also be different than theconfiguration of the backhaul link of the UE relay.

FIG. 15 is a conceptual data flow diagram 1500 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 1502. The apparatus may be a UE, and may be a UE configured toperform any of the steps described in connection with FIG. 12. Theapparatus includes a receiving module 1504, a monitoring module 1506, aselection module 1508, and a transmission module 1510.

The receiving module 1504 receives an LDCS configuration for a UE relay1550 a from a second entity, e.g., a cell or another LPN, 1550 b. Thus,although not illustrated, the LPN may comprise an LPN such as a RRH orUE relay. The monitoring module 1506 monitors for an LDCS from the UErelay based on the received LDCS configuration. The LDCS will bereceived by the receiving module 1504 and communicated from thereceiving module 1504 to the monitoring module 1506.

Although only a single UE relay 1550 a and second 1550 b entity areillustrated, the receiving module 1504 may receive LDCS configurationsfor a plurality of LPNs, the plurality of LPNs include the UE relay, andthe monitoring module 1506 may monitor for a plurality of LDCSs from theplurality of LPNs based on the received LDCS configurations.

The selecting module 1508 selects one of the LPNs, e.g., among theplurality of LPNs based on any of the received backhaul qualityinformation, the received loading capability information, a receivedsignal strength, and a path loss for the corresponding LPN. Thisinformation may be received from the receiving module or the monitoringmodule. The selecting module may determine a buffer status at the UE anddetermine whether to access any of the plurality of LPNs based on atleast one of the received backhaul quality information and the loadingcapability information for the corresponding LPN in combination with thedetermined buffer status of the UE.

The transmission module transmits, among other things, an RACH messageto the selected LPN at an RACH delay after receiving the LDCS from theselected LPN. Thus, based on the output from the selection module, thetransmission module transmits the RACH. Additionally, the transmissionmodule 1510 may receive the RACH delay for the transmission, e.g., fromthe monitoring module 1506. The RACH delay may be signaled to the UEfrom either the UE relay or the second entity.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow chart of FIG. 12. Assuch, each step in the aforementioned flow chart of FIG. 12 may beperformed by a module and the apparatus may include one or more of thosemodules. The modules may be one or more hardware components specificallyconfigured to carry out the stated processes/algorithm, implemented by aprocessor configured to perform the stated processes/algorithm, storedwithin a computer-readable medium for implementation by a processor, orsome combination thereof.

FIG. 16 is a diagram 1600 illustrating an example of a hardwareimplementation for an apparatus 1502′ employing a processing system1614. The processing system 1614 may be implemented with a busarchitecture, represented generally by the bus 1624. The bus 1624 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1614 and the overalldesign constraints. The bus 1624 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 1604, the modules 1504, 1506, 1508, 1510 and thecomputer-readable medium 1606. The bus 1624 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1614 may be coupled to a transceiver 1610. Thetransceiver 1610 is coupled to one or more antennas 1620. Thetransceiver 1610 provides a means for communicating with various otherapparatus over a transmission medium. The processing system 1614includes a processor 1604 coupled to a computer-readable medium 1606.The processor 1604 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1606. Thesoftware, when executed by the processor 1604, causes the processingsystem 1614 to perform the various functions described supra for anyparticular apparatus. The computer-readable medium 1606 may also be usedfor storing data that is manipulated by the processor 1604 whenexecuting software. The processing system further includes at least oneof the modules 1504, 1506, 1508, and 1510. The modules may be softwaremodules running in the processor 1604, resident/stored in the computerreadable medium 1606, one or more hardware modules coupled to theprocessor 1604, or some combination thereof. The processing system 1614may be a component of the UE 650 and may include the memory 660 and/orat least one of the TX processor 668, the RX processor 656, and thecontroller/processor 659.

In one configuration, the apparatus 1502/1502′ for wirelesscommunication includes means for means for receiving a very low dutycycle signal (LDCS) configuration for a UE relay from a second entity,means for monitoring for an LDCS from the UE relay based on the receivedLDCS configuration, means for selecting an LPN among a plurality ofLPNs, and means for transmitting an RACH. The aforementioned means maybe one or more of the aforementioned modules of the apparatus 1502and/or the processing system 1614 of the apparatus 1502′ configured toperform the functions recited by the aforementioned means. As describedsupra, the processing system 1614 may include the TX Processor 668, theRX Processor 656, and the controller/processor 659. As such, in oneconfiguration, the aforementioned means may be the TX Processor 668, theRX Processor 656, and the controller/processor 659 configured to performthe functions recited by the aforementioned means.

FIG. 17 is a conceptual data flow diagram 1700 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 1702. The apparatus transmits an LDCS configuration of a UErelay. Among others, the apparatus may be another LPN that is not in adormant mode and a cell. The apparatus includes a receiving module 1704,an identifying module 1706, a determining module 1708, and atransmission module 1710.

The identifying module 1706 identifies a UE relay 1750 a. Thetransmission module transmits an LDCS configuration for the UE relay1750 a to a UE 1750 b. The LDCS configuration may be based on LDCSinformation received at the receiving module 1704 regarding the LDCS, orit may be determined at apparatus 1702 itself via the determinationmodule 1708. The transmission module further transmits LDCSconfiguration to the UE relay 1750 a when the apparatus 1702 determinesthe configuration itself.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow charts of FIG. 13. Assuch, each step in the aforementioned flow charts of FIG. 13 may beperformed by a module and the apparatus may include one or more of thosemodules. The modules may be one or more hardware components specificallyconfigured to carry out the stated processes/algorithm, implemented by aprocessor configured to perform the stated processes/algorithm, storedwithin a computer-readable medium for implementation by a processor, orsome combination thereof.

FIG. 18 is a diagram 1800 illustrating an example of a hardwareimplementation for an apparatus 1702′ employing a processing system1814. The processing system 1814 may be implemented with a busarchitecture, represented generally by the bus 1824. The bus 1824 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 1814 and the overalldesign constraints. The bus 1824 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 1804, the modules 1704, 1706, 1708, 1710, and thecomputer-readable medium 1806. The bus 1824 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 1814 may be coupled to a transceiver 1810. Thetransceiver 1810 is coupled to one or more antennas 1820. Thetransceiver 1810 provides a means for communicating with various otherapparatus over a transmission medium. The processing system 1814includes a processor 1804 coupled to a computer-readable medium 1806.The processor 1804 is responsible for general processing, including theexecution of software stored on the computer-readable medium 1806. Thesoftware, when executed by the processor 1804, causes the processingsystem 1814 to perform the various functions described supra for anyparticular apparatus. The computer-readable medium 1806 may also be usedfor storing data that is manipulated by the processor 1804 whenexecuting software. The processing system further includes at least oneof the modules 1704, 1706, 1708, and 1710. The modules may be softwaremodules running in the processor 1804, resident/stored in the computerreadable medium 1806, one or more hardware modules coupled to theprocessor 1804, or some combination thereof. The processing system 1814may be a component of the eNB 610 and may include the memory 676 and/orat least one of the TX processor 616, the RX processor 670, and thecontroller/processor 675. The processing system 1814 may be a componentof the UE 650 and may include the memory 660 and/or at least one of theTX processor 668, the RX processor 656, and the controller/processor659.

In one configuration, the apparatus 1702/1702′ for wirelesscommunication includes means for means for identifying a UE relay, meansfor transmitting an LDCS configuration of at least one UE relay, meansfor receiving LDCS information for the UE relay, and means fordetermining, among other things, the LDCS configuration. Theaforementioned means may be one or more of the aforementioned modules ofthe apparatus 1702 and/or the processing system 1814 of the apparatus1702′ configured to perform the functions recited by the aforementionedmeans. As described supra, the processing system 1814 may include the TXProcessor 616, the RX Processor 670, and the controller/processor 675.As such, in one configuration, the aforementioned means may be the TXProcessor 616, the RX Processor 670, and the controller/processor 675configured to perform the functions recited by the aforementioned means.The aforementioned means may also be one or more of the aforementionedmodules of the apparatus 1702 and/or the processing system 1814 of theapparatus 1702′ configured to perform the functions recited by theaforementioned means. As described supra, the processing system 1814 mayinclude the TX Processor 668, the RX Processor 656, and thecontroller/processor 659. As such, in one configuration, theaforementioned means may be the TX Processor 668, the RX Processor 656,and the controller/processor 659 configured to perform the functionsrecited by the aforementioned means.

FIG. 19 is a conceptual data flow diagram 1900 illustrating the dataflow between different modules/means/components in an exemplaryapparatus 1902. The apparatus may be an LPN, e.g., a UE relay. Theapparatus includes a transitioning module 1904, a transmission module1906, a determining module 1908, a receiving module 1910, and amonitoring module 1912.

The transitioning module 1904 transitions the UE relay to a differentstate, such as a dormant state. The transitioning module may alsotransition the UE relay to an active state and to a DRX/DTX state. Thetransmission module 1906 transmits an LDCS while the UE relay is in thedormant state. The monitoring module 1912 monitors for an RACH message,e.g., at a predetermined RACH delay, and monitors UE associated with theUE relay. For example, the monitoring module monitors any connected UEsand any active UEs. The determining module 1908 determines theconnection and/or active status of UEs for the UE relay. The determiningmodule also matches the DRX/DTX mode to other DRX/DTX modes.

The apparatus may include additional modules that perform each of thesteps of the algorithm in the aforementioned flow charts of FIG. 14. Assuch, each step in the aforementioned flow charts of FIG. 14 may beperformed by a module and the apparatus may include one or more of thosemodules. The modules may be one or more hardware components specificallyconfigured to carry out the stated processes/algorithm, implemented by aprocessor configured to perform the stated processes/algorithm, storedwithin a computer-readable medium for implementation by a processor, orsome combination thereof.

FIG. 20 is a diagram 2000 illustrating an example of a hardwareimplementation for an apparatus 1902′ employing a processing system2014. The processing system 2014 may be implemented with a busarchitecture, represented generally by the bus 2024. The bus 2024 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 2014 and the overalldesign constraints. The bus 2024 links together various circuitsincluding one or more processors and/or hardware modules, represented bythe processor 2004, the modules 1904, 1906, 1908, 1910, 1912, and thecomputer-readable medium 2006. The bus 2024 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The processing system 2014 may be coupled to a transceiver 2010. Thetransceiver 2010 is coupled to one or more antennas 2020. Thetransceiver 2010 provides a means for communicating with various otherapparatus over a transmission medium. The processing system 2014includes a processor 2004 coupled to a computer-readable medium 2006.The processor 2004 is responsible for general processing, including theexecution of software stored on the computer-readable medium 2006. Thesoftware, when executed by the processor 2004, causes the processingsystem 2014 to perform the various functions described supra for anyparticular apparatus. The computer-readable medium 2006 may also be usedfor storing data that is manipulated by the processor 2004 whenexecuting software. The processing system further includes at least oneof the modules 1904, 1906, 1908, 1910, and 1912. The modules may besoftware modules running in the processor 2004, resident/stored in thecomputer readable medium 2006, one or more hardware modules coupled tothe processor 2004, or some combination thereof. The processing system2014 may be a component of the eNB 610 and may include the memory 676and/or at least one of the TX processor 616, the RX processor 670, andthe controller/processor 675. The processing system 2014 may be acomponent of the UE 650 and may include the memory 660 and/or at leastone of the TX processor 668, the RX processor 656, and thecontroller/processor 659.

In one configuration, the apparatus 1902/1902′ for wirelesscommunication includes means for means for transitioning to a dormantstate, means for transmitting an LDCS while in the dormant state, meansfor monitoring for a RACH message at a predetermined RACH delay aftertransmitting the LDCS, means for monitoring at least one connected UE,means for determining whether any connected UE is active, and means formatching the DRX/DTX mode of the UE relay to a DRX/DTX mode for at leastone connected UE. The aforementioned means may be one or more of theaforementioned modules of the apparatus 1902 and/or the processingsystem 2014 of the apparatus 1902′ configured to perform the functionsrecited by the aforementioned means. As described supra, the processingsystem 2014 may include the TX Processor 616, the RX Processor 670, andthe controller/processor 675. As such, in one configuration, theaforementioned means may be the TX Processor 616, the RX Processor 670,and the controller/processor 675 configured to perform the functionsrecited by the aforementioned means. The aforementioned means may alsobe one or more of the aforementioned modules of the apparatus 1902and/or the processing system 2014 of the apparatus 1902′ configured toperform the functions recited by the aforementioned means. As describedsupra, the processing system 2014 may include the TX Processor 668, theRX Processor 656, and the controller/processor 659. As such, in oneconfiguration, the aforementioned means may be the TX Processor 668, theRX Processor 656, and the controller/processor 659 configured to performthe functions recited by the aforementioned means.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Further, somesteps may be combined or omitted. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. All structural andfunctional equivalents to the elements of the various aspects describedthroughout this disclosure that are known or later come to be known tothose of ordinary skill in the art are expressly incorporated herein byreference and are intended to be encompassed by the claims. Moreover,nothing disclosed herein is intended to be dedicated to the publicregardless of whether such disclosure is explicitly recited in theclaims. No claim element is to be construed as a means plus functionunless the element is expressly recited using the phrase “means for.”

What is claimed is:
 1. A method of wireless communication at a userequipment (UE), comprising: receiving a very low duty cycle signal(LDCS) configuration for a user equipment Relay (UE Relay) from a secondentity; and monitoring for an LDCS from the UE Relay based on thereceived LDCS configuration.
 2. The method of claim 1, wherein thesecond entity comprises one of a low power node (LPN) that is not in adormant state and a Macro cell.
 3. The method of claim 1, wherein theformat of the LDCS comprises at least one of a special synchronizationsignal format, an enhanced cell-specific reference signal (CRS) format,a coded signal transmission format, a channel state informationreference signal (CSI-RS) format, and a system information block (SIB)format.
 4. The method of claim 2, wherein the format of the LDCScomprises a system information block (SIB) format having a reducedamount of information, wherein the LDCS comprises at least one of SIBinformation and a global cell ID.
 5. The method of claim 2, wherein theformat of the LDCS comprises an enhanced cell-specific reference signal(CRS) having a low duty cycle and spans any of five resource blocks(RB), 25 RB, and the entire system bandwidth.
 6. The method of claim 2,wherein the format of the LDCS comprises a coded signal transmissionhaving a low re-use preamble comprising encoded information of at leasta global cell ID.
 7. The method of claim 1, wherein the LDCSconfiguration is comprised in at least one of a primary synchronizationsignal (PSS) transmission, a secondary synchronization signal (SSS)transmission, a physical broadcast channel (PBCH) transmission, a systeminformation block (SIB) transmission, and a master information block(MIB) transmission from the second entity.
 8. The method of claim 1,wherein the UE monitors for the LDCS during at least one of an idle modein order to perform cell reselection and an active mode in order toperform a possible data connection through the UE relay.
 9. The methodof claim 8, further comprising: receiving LDCS configurations for aplurality of low power nodes (LPNs), the plurality of LPNs including theUE relay, wherein the UE monitors for a plurality of LDCSs from theplurality of LPNs based on the received LDCS configurations; and whenthe UE determines a need to connect to a LPN, selecting an LPN among theplurality of LPNs based on at least one of a largest received poweramong the monitored LDCSs and a smallest path loss among the monitoredLDCSs.
 10. The method of claim 9, wherein the LPN is selected based on asmallest path loss among the monitored LDCSs.
 11. The method of claim 9,further comprising: receiving a transmit power for the plurality of LPNsfrom the second entity, wherein the transmit power for each of the LPNsis comprised in the received LDCS configuration for the correspondingLPN; and determining a path loss for each of the plurality of LPNs basedat least in part on the received transmit power for the correspondingLPNs.
 12. The method of claim 9, wherein each LDCS comprises a transmitpower for the corresponding LPN, the method further comprising:determining a path loss for each of the plurality of LPNs based at leastin part on the received transmit power for the corresponding LPN. 13.The method of claim 9, further comprising: transmitting a Random AccessChannel (RACH) message to the selected LPN at an RACH delay afterreceiving the LDCS from the selected LPN, wherein the RACH delay iscomprised in at least one of the LDCS received from the selected LPN andthe LDCS configuration received from the second entity.
 14. The methodof claim 13, wherein the RACH message is transmitted to the selected LPNusing an RACH configuration linked to the selected LPN after receivingthe LDCS from the selected LPN, wherein the RACH configuration iscomprised in at least one of the LDCS received from the selected LPN andthe LDCS configuration received from the second entity.
 15. The methodof claim 1, further comprising: receiving an LDCS from a plurality oflow power nodes (LPNs), based on the received LDCS configurations fromthe second entity, wherein the LDCS for each of the LPNs comprises atleast one of backhaul quality information and loading capabilityinformation for the corresponding LPN.
 16. The method of claim 15,further comprising: determining a buffer status at the UE; anddetermining whether to access any of the plurality of LPNs based on atleast one of the received backhaul quality information and the loadingcapability information for the corresponding LPN in combination with thedetermined buffer status of the UE.
 17. The method of claim 15, furthercomprising: determining whether to access any of the plurality of LPNsbased on any of the received backhaul quality information, the receivedloading capability information, a received signal strength, and a pathloss for the corresponding LPN.
 18. An apparatus for wirelesscommunication, comprising: means for receiving a very low duty cyclesignal (LDCS) configuration for a user equipment Relay (UE Relay) from asecond entity; and means for monitoring for an LDCS from the UE Relaybased on the received LDCS configuration.
 19. The apparatus of claim 18,wherein the second entity comprises one of a low power node (LPN), thatis not in a dormant state and a Macro cell.
 20. The apparatus of claim18, wherein the format of the LDCS comprises at least one of a specialsynchronization signal format, an enhanced cell-specific referencesignal (CRS) format, a coded signal transmission format, a channel stateinformation reference signal (CSI-RS) format, and a system informationblock (SIB) format.
 21. The apparatus of claim 19, wherein the format ofthe LDCS comprises a system information block (SIB) format having areduced amount of information, wherein the LDCS comprises at least oneof SIB information and a global cell ID.
 22. The apparatus of claim 19,wherein the format of the LDCS comprises an enhanced cell-specificreference signal (CRS) having a low duty cycle and spans any of fiveresource blocks (RB), 25 RB, and the entire system bandwidth.
 23. Theapparatus of claim 19, wherein the format of the LDCS comprises a codedsignal transmission having a low re-use preamble comprising encodedinformation of at least a global cell ID.
 24. The apparatus of claim 18,wherein the LDCS configuration is comprised in at least one of a primarysynchronization signal (PSS) transmission, a secondary synchronizationsignal (SSS) transmission, a physical broadcast channel (PBCH)transmission, a system information block (SIB) transmission, and amaster information block (MIB) transmission from the second entity. 25.The apparatus of claim 18, wherein the apparatus monitors for the LDCSduring at least one of an idle mode in order to perform cell reselectionand an active mode in order to perform a possible data connectionthrough the UE relay.
 26. The apparatus of claim 25, wherein the meansfor receiving receive LDCS configurations for a plurality of low powernodes (LPNs), the plurality of LPNs including the UE relay, wherein theapparatus monitors for a plurality of LDCSs from the plurality of LPNsbased on the received LDCS configurations, the apparatus furthercomprising: means for selecting an LPN among the plurality of LPNs basedon at least one of a largest received power among the monitored LDCSsand a smallest path loss among the monitored LDCSs, when the apparatusdetermines a need to connect to a LPN.
 27. The apparatus of claim 26,wherein the LPN is selected based on a smallest path loss among themonitored LDCSs.
 28. The apparatus of claim 26, wherein the means forreceiving receives a transmit power for the plurality of LPNs from thesecond entity, wherein the transmit power for each of the LPNs iscomprised in the received LDCS configuration for the corresponding LPN,and wherein the means for selecting determines a path loss for each ofthe plurality of LPNs based at least in part on the received transmitpower for the corresponding LPNs.
 29. The apparatus of claim 26, whereineach LDCS comprises a transmit power for the corresponding LPN, andwherein the means for selecting determines a path loss for each of theplurality of LPNs based at least in part on the received transmit powerfor the corresponding LPN.
 30. The apparatus of claim 26, furthercomprising: means for transmitting a Random Access Channel (RACH)message to the selected LPN at an RACH delay after receiving the LDCSfrom the selected LPN, wherein the RACH delay is comprised in at leastone of the LDCS received from the selected LPN and the LDCSconfiguration received from the second entity.
 31. The apparatus ofclaim 30, wherein the RACH message is transmitted to the selected LPNusing an RACH configuration linked to the selected LPN after receivingthe LDCS from the selected LPN, wherein the RACH configuration iscomprised in at least one of the LDCS received from the selected LPN andthe LDCS configuration received from the second entity.
 32. Theapparatus of claim 18, wherein the means for receiving receives an LDCSfrom a plurality of low power nodes (LPNs) based on the received LDCSconfigurations from the second entity, wherein the LDCS for each of theLPNs comprises at least one of backhaul quality information and loadingcapability information for the corresponding LPN.
 33. The apparatus ofclaim 32, further comprising: means for selecting an LPN among theplurality of LPNs, wherein the means for selecting determines a bufferstatus at the apparatus and determines whether to access any of theplurality of LPNs based on at least one of the received backhaul qualityinformation and the loading capability information for the correspondingLPN in combination with the determined buffer status of the apparatus.34. The apparatus of claim 32, wherein the means for selectingdetermines whether to access any of the plurality of LPNs based on anyof the received backhaul quality information, the received loadingcapability information, a received signal strength, and a path loss forthe corresponding LPN.
 35. An apparatus for wireless communication,comprising: a processing system configured to: receive a very low dutycycle signal (LDCS) configuration for a user equipment Relay (UE Relay)from a second entity; and monitor for an LDCS from the UE Relay based onthe received LDCS configuration.
 36. The apparatus of claim 35, whereinthe second entity comprises one of a low power node (LPN) that is not ina dormant state and a Macro cell.
 37. The apparatus of claim 35, whereinthe format of the LDCS comprises at least one of a specialsynchronization signal format, an enhanced cell-specific referencesignal (CRS) format, a coded signal transmission format, a channel stateinformation reference signal (CSI-RS) format, and a system informationblock (SIB) format.
 38. The apparatus of claim 36, wherein the format ofthe LDCS comprises a system information block (SIB) format having areduced amount of information, wherein the LDCS comprises at least oneof SIB information and a global cell ID.
 39. The apparatus of claim 36,wherein the format of the LDCS comprises an enhanced cell-specificreference signal (CRS) having a low duty cycle and spans any of fiveresource blocks (RB), 25 RB, and the entire system bandwidth.
 40. Theapparatus of claim 36, wherein the format of the LDCS comprises a codedsignal transmission having a low re-use preamble comprising encodedinformation of at least a global cell ID.
 41. The apparatus of claim 35,wherein the LDCS configuration is comprised in at least one of a primarysynchronization signal (PSS) transmission, a secondary synchronizationsignal (SSS) transmission, a physical broadcast channel (PBCH)transmission, a system information block (SIB) transmission, and amaster information block (MIB) transmission from the second entity. 42.The apparatus of claim 35, wherein the apparatus monitors for the LDCSduring at least one of an idle mode in order to perform cell reselectionand an active mode in order to perform a possible data connectionthrough the UE relay.
 43. The apparatus of claim 42, wherein theprocessing system is further configured to: receive LDCS configurationsfor a plurality of low power nodes (LPNs), the plurality of LPNsincluding the UE relay, wherein the apparatus monitors for a pluralityof LDCSs from the plurality of LPNs based on the received LDCSconfigurations; and when the apparatus determines a need to connect to aLPN, select an LPN among the plurality of LPNs based on at least one ofa largest received power among the monitored LDCSs and a smallest pathloss among the monitored LDCSs.
 44. The apparatus of claim 43, whereinthe LPN is selected based on a smallest path loss among the monitoredLDCSs.
 45. The apparatus of claim 43, wherein the processing system isfurther configured to: receive a transmit power for the plurality ofLPNs from the second entity, wherein the transmit power for each of theLPNs is comprised in the received LDCS configuration for thecorresponding LPN; and determine a path loss for each of the pluralityof LPNs based at least in part on the received transmit power for thecorresponding LPNs.
 46. The apparatus of claim 43, wherein each LDCScomprises a transmit power for the corresponding LPN, and wherein theprocessing system is further configured to: determine a path loss foreach of the plurality of LPNs based at least in part on the receivedtransmit power for the corresponding LPN.
 47. The apparatus of claim 43,wherein the processing system is further configured to: transmit aRandom Access Channel (RACH) message to the selected LPN at an RACHdelay after receiving the LDCS from the selected LPN, wherein the RACHdelay is comprised in at least one of the LDCS received from theselected LPN and the LDCS configuration received from the second entity.48. The apparatus of claim 47, wherein the RACH message is transmittedto the selected LPN using an RACH configuration linked to the selectedLPN after receiving the LDCS from the selected LPN, wherein the RACHconfiguration is comprised in at least one of the LDCS received from theselected LPN and the LDCS configuration received from the second entity.49. The apparatus of claim 35, wherein the processing system is furtherconfigured to: receive an LDCS from a plurality of low power nodes(LPNs) based on the received LDCS configurations from the second entity,wherein the LDCS for each of the LPNs comprises at least one of backhaulquality information and loading capability information for thecorresponding LPN.
 50. The apparatus of claim 49, wherein the processingsystem is further configured to: determine a buffer status at theapparatus; and determine whether to access any of the plurality of LPNsbased on at least one of the received backhaul quality information andthe loading capability information for the corresponding LPN incombination with the determined buffer status of the apparatus.
 51. Theapparatus of claim 49, wherein the processing system is furtherconfigured to: determine whether to access any of the plurality of LPNsbased on any of the received backhaul quality information, the receivedloading capability information, a received signal strength, and a pathloss for the corresponding LPN.
 52. A computer program product,comprising: a computer-readable medium comprising code for: receiving avery low duty cycle signal (LDCS) configuration for a user equipmentRelay (UE Relay) from a second entity; and monitoring for an LDCS fromthe UE Relay based on the received LDCS configuration.
 53. The computerprogram product of claim 52, wherein the second entity comprises one ofa low power node (LPN) that is not in a dormant state and a Macro cell.54. The computer program product of claim 52, wherein the format of theLDCS comprises at least one of a special synchronization signal format,an enhanced cell-specific reference signal (CRS) format, a coded signaltransmission format, a channel state information reference signal(CSI-RS) format, and a system information block (SIB) format.
 55. Thecomputer program product of claim 53, wherein the format of the LDCScomprises a system information block (SIB) format having a reducedamount of information, wherein the LDCS comprises at least one of SIBinformation and a global cell ID.
 56. The computer program product ofclaim 53, wherein the format of the LDCS comprises an enhancedcell-specific reference signal (CRS) having a low duty cycle and spansany of five resource blocks (RB), 25 RB, and the entire systembandwidth.
 57. The computer program product of claim 53, wherein theformat of the LDCS comprises a coded signal transmission having a lowre-use preamble comprising encoded information of at least a global cellID.
 58. The computer program product of claim 52, wherein the LDCSconfiguration is comprised in at least one of a primary synchronizationsignal (PSS) transmission, a secondary synchronization signal (SSS)transmission, a physical broadcast channel (PBCH) transmission, a systeminformation block (SIB) transmission, and a master information block(MIB) transmission from the second entity.
 59. The computer programproduct of claim 52, wherein the UE monitors for the LDCS during atleast one of an idle mode in order to perform cell reselection and anactive mode in order to perform a possible data connection through theUE relay.
 60. The computer program product of claim 59, furthercomprising code for: receiving LDCS configurations for a plurality oflow power nodes (LPNs), the plurality of LPNs including the UE relay,wherein a user equipment (UE) monitors for a plurality of LDCSs from theplurality of LPNs based on the received LDCS configurations; and whenthe UE determines a need to connect to a LPN, selecting an LPN among theplurality of LPNs based on at least one of a largest received poweramong the monitored LDCSs and a smallest path loss among the monitoredLDCSs.
 61. The computer program product of claim 60, wherein the LPN isselected based on a smallest path loss among the monitored LDCSs. 62.The computer program product of claim 60, further comprising code for:receiving a transmit power for the plurality of LPNs from the secondentity, wherein the transmit power for each of the LPNs is comprised inthe received LDCS configuration for the corresponding LPN; anddetermining a path loss for each of the plurality of LPNs based at leastin part on the received transmit power for the corresponding LPNs. 63.The computer program product of claim 60, wherein each LDCS comprises atransmit power for the corresponding LPN, the method further comprising:determining a path loss for each of the plurality of LPNs based at leastin part on the received transmit power for the corresponding LPN. 64.The computer program product of claim 60, further comprising code for:transmitting a Random Access Channel (RACH) message to the selected LPNat an RACH delay after receiving the LDCS from the selected LPN, whereinthe RACH delay is comprised in at least one of the LDCS received fromthe selected LPN and the LDCS configuration received from the secondentity.
 65. The computer program product of claim 64, wherein the RACHmessage is transmitted to the selected LPN using an RACH configurationlinked to the selected LPN after receiving the LDCS from the selectedLPN, wherein the RACH configuration is comprised in at least one of theLDCS received from the selected LPN and the LDCS configuration receivedfrom the second entity.
 66. The computer program product of claim 52,further comprising code for: receiving an LDCS from a plurality of lowpower nodes (LPNs) based on the received LDCS configurations from thesecond entity, wherein the LDCS for each of the LPNs comprises at leastone of backhaul quality information and loading capability informationfor the corresponding LPN.
 67. The computer program product of claim 66,further comprising code for: determining a buffer status at the UE; anddetermining whether to access any of the plurality of LPNs based on atleast one of the received backhaul quality information and the loadingcapability information for the corresponding LPN in combination with thedetermined buffer status of the UE.
 68. The computer program product ofclaim 66, further comprising code for: determining whether to access anyof the plurality of LPNs based on any of the received backhaul qualityinformation, the received loading capability information, a receivedsignal strength, and a path loss for the corresponding LPN.